Radio Transmitter Apparatus, Radio Receiver Apparatus, and Wireless Communication System

ABSTRACT

A wireless communication system capable of obtaining diversity gain without fail even when the distribution of the reception qualities is large. In a radio transmitter apparatus ( 100 ) of the wireless communication system, a repetition/constellation pattern ratio deciding part ( 113 ) adjusts the number of constellations to be used by a modulating part ( 102 ) and also adjusts the number of replicas of a repetition part ( 103 ) in such a manner that the product of the number of constellation patterns to be used by the modulating part ( 102 ), that is, the number of outbound symbols to be generated and the number of outbound symbols as replicated by the repetition part ( 103 ) becomes equal to the number of outbound symbols generated from a single transmission data notified from a control information extracting part ( 112 ).

This is a divisional application of application Ser. No. 11/579,860filed Nov. 8, 2006, which is a national phase under 35 USC 371 ofPCT/JP2005/008198 filed Apr. 28, 2005, which is based on Japaneseapplication number 2004-140968 filed May 11, 2004, the entire contentsof each of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a radio communication system forreplicating transmission data (hereinafter, referred to as “repetition”as appropriate) to be transmitted, and a radio transmission apparatusand radio reception apparatus used in this system.

BACKGROUND ART

Conventionally, in a multicarrier communication system, a technique hasbeen used where a multicarrier communication apparatus on a receivingside combines a last received packet and re-received packet and performsdecoding, thereby obtaining the diversity gain in the time domain andreducing a bit error rate of the packet.

Further, another technique has been developed where a multicarriercommunication apparatus on a transmitting side modulates a packet usinga different constellation pattern from that of the last transmittedpacket when re-transmitting the packet, and exchanges higher-order bitsand lower-order bits of the last transmitted packet to obtain thediversity gain in the time domain, thereby reducing a bit error rate ofthe packet (for example, see Patent Document 1).

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-309535DISCLOSURE OF INVENTION Problems to be Solved by the Present Invention

However, with the technique as described in Patent Document 1, themulticarrier communication apparatus on the receiving side does notobtain the diversity gain in the frequency domain that is derived fromcharacteristics of a multicarrier signal though it obtains the diversitygain in the time domain, and there is therefore room for improving thediversity gain.

Further, in the technique as described in Patent Document 1,higher-order bits and lower-order bits of the last transmitted packetare always exchanged and re-transmitted. Here, a diversity gain has acharacteristic of being obtained more easily in performing symbolcombination than in performing bit combination when the dispersion ofquality of a received signal is large, and being obtained more easily inperforming bit combination than in performing symbol combination whenthe dispersion of the reception quality is small. FIG. 1 shows thischaracteristic in the table. Accordingly, with the technique describedin Patent Document 1, when the dispersion of the reception quality islarge, bit combination is performed on the last transmitted packet andre-received packet in which the higher-order bits and the lower-orderbits of the last transmitted packet are exchanged, and there istherefore a problem that the diversity gain is hard to obtain.

It is therefore an object of the present invention to provide a radiotransmission apparatus, radio reception apparatus and radiocommunication system capable of reliably obtaining the diversity gainwhen the dispersion of reception quality of a received signal is large.

Means for Solving the Problem

In the present invention, a radio transmission apparatus performsmodulation and replication on transmission data using a plurality ofconstellation patterns to generate a plurality of transmission symbols,and transmits the generated plurality of transmission symbols in asingle multicarrier signal by radio, and a radio reception apparatusperforms symbol combination and bit combination on the receivedmulticarrier signal.

ADVANTAGEOUS EFFECT OF THE PRESENT INVENTION

According to the present invention even when the dispersion of receptionquality of a multicarrier signal is large in the radio receptionapparatus, it is possible to reliably obtain the diversity gain in thefrequency domain.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a table showing a characteristic of the diversity gain;

FIG. 2 is a block diagram illustrating a configuration of a radiotransmission apparatus according to one embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating a configuration of a radioreception apparatus according to one embodiment of the presentinvention;

FIG. 4 is a diagram showing a flow of signal processing according to oneembodiment of the present invention;

FIG. 5 is a diagram showing an example of modulation setting accordingto one embodiment of the present invention;

FIG. 6A is a view showing combinations of constellation patternsaccording to one embodiment of the present invention;

FIG. 6B is a view showing other combinations of constellation patternsaccording to one embodiment of the present invention; and

FIG. 6C is a view showing still other combinations of constellationpatterns according to one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

An embodiment of the present invention will be described below in detailwith reference to the accompanying drawings. In the followingdescriptions, a transmitting side of a multicarrier signal is referredto as a radio transmission apparatus, and a receiving side of themulticarrier signal is referred to as a radio reception apparatus.

FIG. 2 is a block diagram illustrating a configuration of radiotransmission apparatus 100 according to one embodiment of the presentinvention.

FIG. 3 is a block diagram illustrating a configuration of radioreception apparatus 150 according to one embodiment of the presentinvention. Radio transmission apparatus 100 is installed in a basestation apparatus, for example. Radio reception apparatus 150 isinstalled in a communication terminal apparatus such as a cellulartelephone. Further, radio transmission apparatus 100 and radio receptionapparatus 150 are components of a radio communication system such as amobile communication system.

Radio transmission apparatus 100 as shown in FIG. 2 has: errorcorrection coding section 101, modulation section 102; repetitionsection 103; serial/parallel (S/P) section 104; symbol interleavingsection 105, inverse fast Fourier transform (IFFT) section 106; guardinterval (GI) inserting section 107; transmission radio frequency (RF)section 108; antenna element 109; reception RF section 111; controlinformation extracting section 112; repetition/constellation patternratio determining section 113; constellation pattern instructing section114; and number of repetitions instructing section 115.

Error correction coding section 101 performs error correction coding ontransmission data inputted from, for example, a baseband section (notshown) at a predetermined coding rate, for example, R=1/3, and inputsthe transmission data after error correction coding to modulationsection 102.

Modulation section 102 modulates the transmission data inputted fromerror correction coding section 101 using a modulation scheme andconstellation pattern specified by constellation pattern instructingsection 114 (described later) to generate a transmission symbol. Forexample, if modulation section 102 is instructed to use twoconstellation patterns in 16QAM by constellation pattern instructingsection 114, modulation section 102 modulates the transmission datainputted from error correction coding section 101 using these twoconstellation patterns and generates two transmission symbols. Then,modulation section 102 inputs the generated transmission symbols torepetition section 103. Modulation section 102 is able to use allconstellation patterns in such as QPSK (Quadrature Phase Shift Keying),16QAM (Quadrature Amplitude Modulation), 64QAM, and 256QAM.

Repetition section 103 replicates the transmission symbols inputted frommodulation section 102 up to the number of replications instructed bynumber of repetitions instructing section 115 (described later), andinputs the replicated transmission symbols to S/P section 104.Accordingly, modulation section 102 and repetition section 103constitute a modulation/replication section.

S/P section 104 converts the transmission symbols inputted fromrepetition section 103 from a serial signal into a parallel signal, andinputs the parallel signal to symbol interleaving section 105.

Symbol interleaving section 105 interleaves the parallel signal inputtedfrom S/P section 104 on a symbol basis, and inputs the interleavedparallel signal to IFFT section 106.

IFFT section 106 performs inverse fast Fourier transform on the parallelsignal inputted from symbol interleaving section 105, thereby generatingan OFDM (Orthogonal Frequency Division Multiplexing) signal that is amulticarrier signal. Then, IFFT section 106 inputs the generated OFDMsignal to GI inserting section 107.

GI inserting section 107 inserts a GI into the generated OFDM signalinputted from IFFT section 106, and inputs the OFDM signal after the GIinsertion to transmission RF section 108.

Transmission RF section 108 has, for example, a digital/analogconverter, low noise amplifier, and band pass filter, performspredetermined radio transmission processing on the OFDM signal inputtedfrom GI inserting section 107, and transmits the radio OFDM signal afterprocessing to radio reception apparatus 150 via antenna element 109. Inaddition, transmission RF section 108 reports the number ofconstellation patterns used in modulation section 102 and the number ofreplications by repetition section 103 with respect to the OFDM signalto be transmitted, to radio reception apparatus 150 using a controlchannel.

Reception RF section 111 has, for example, an analog/digital converter,low noise amplifier, band pass filter, and performs predetermined radioreception processing on a control information signal from radioreception apparatus 150 received by antenna element 109. This controlinformation signal will be described later. Then, reception RF section111 inputs the control information signal after the radio receptionprocessing to control information extracting section 112.

Control information extracting section 112 extracts information of themodulation scheme determined in radio reception apparatus 150,information of the number of transmission symbols generated from an itemof transmission data determined in radio reception apparatus 150, andinformation of the dispersion of reception quality measured in radioreception apparatus 150 from the control information signal inputtedfrom reception RF section 111, and reports each extracted information torepetition/constellation pattern ratio determining section 113.

Based on the dispersion of reception quality reported from controlinformation extracting section 112, repetition/constellation patternratio determining section 113 determines a ratio between the number ofconstellation patterns to be used in modulation section 102 and thenumber of replications by repetition section 103. More specifically,repetition/constellation pattern ratio determining section 113 adjuststhe number of constellation patterns to be used in modulation section102 and the number of replications by repetition section 103 so that theproduct of the number of constellation patterns used in modulationsection 102, that is, the number of generated transmission symbols andthe number of replications of that transmission symbols by repetitionsection 103 is the number of transmission symbols generated from an itemof transmission data reported from control information extractingsection 112. Further, when adjusting the number of constellationpatterns to be used in modulation section 102 and the number ofreplications by repetition section 103, repetition/constellation patternratio determining section 113 makes adjustments to decrease the numberof constellation patterns to be used in modulation section 102 when thedispersion of reception quality reported from control informationextracting section 112 increases, and increase the number ofconstellation patterns to be used in modulation section 102 when thedispersion of reception quality decreases. Then,repetition/constellation pattern ratio determining section 113 reportsthe determined number of constellation patterns and the modulationscheme reported from control information extracting section 112 toconstellation pattern instructing section 114, and further reports thedetermined number of replications to number of repetitions instructingsection 115.

Based on the modulation scheme and the number of constellation patternsreported from repetition/constellation pattern ratio determining section113, constellation pattern instructing section 114 reports allconstellation patterns included in a combination of constellationpatterns corresponding to the modulation scheme and the number ofconstellation patterns to modulation section 102, and instructsmodulation section 120 to generate transmission symbols using all theconstellation patterns.

In synchronization with a timing at which a transmission symbol is inputto repetition section 103 from modulation section 102, number ofrepetitions instructing section 115 reports the number of replicationsreported from repetition/constellation pattern ratio determining section113 to repetition section 103, and instructs repetition section 103 toreplicate the transmission symbol up to the number of replications.

Meanwhile, radio reception apparatus 150 as shown in FIG. 3 has antennaelement 151, reception RF section 152, GI removing section 153, fastFourier transform (FFT) section 154, reception quality measuring section155, reception quality dispersion measuring section 156, MCS (Modulationand Coding Scheme) determining section 157, symbol combination/bitcombination instructing section 158, number of symbols for combinationinstructing section 159, constellation pattern instructing section 161,symbol deinterleaving section 162, symbol combining section 163, bitlikelihood calculating section 164, error correction decoding section165, control information generating section 166 and transmission RFsection 167.

Reception RF section 152 has, for example, an analog/digital converter,low noise amplifier, and band pass filter, performs predetermined radioreception processing on the OFDM signal from radio transmissionapparatus 100 received in antenna element 151, and inputs the OFDMsignal after the radio reception processing to GI removing section 153.Reception RF section 152 further performs radio reception processing onthe control channel signal from radio transmission apparatus 100received by antenna element 151, and inputs the control channel signalafter the radio reception processing to symbol combination/bitcombination instructing section 158.

GI removing section 153 removes a GI from the OFDM signal inputted fromreception RF section 152, and inputs the OFDM signal from which the GIis removed to FFT section 154.

FFT section 154 performs FFT processing on the OFDM signal inputted fromGI removing section 153 and generates a reception symbol (parallelsignal). Then, FFT section 154 inputs the generated reception symbol toreception quality measuring section 155 and symbol deinterleavingsection 162.

Reception quality measuring section 155 measures reception quality, thatis, a reception SIR (Signal to Interference Rate) of the receptionsymbol inputted from FFT section 154 on the basis of a symbol of an OFDMsignal basis, and reports the measurement result to reception qualitydispersion measuring section 156 and MCS determining section 157.

Based on the reception quality of the reception symbol inputted fromreception quality measuring section 155, reception quality dispersionmeasuring section 156 measures dispersion of the reception quality, andreports the measurement result to control information generating section166.

Based on the measurement result of the reception quality reported fromreception quality measuring section 155, MCS determining section 157determines a modulation scheme to be used in radio transmissionapparatus 100. In other words, as the reception quality reported fromreception quality measuring section 155 is higher, MCS determiningsection 157 allows radio transmission apparatus 100 to use a modulationscheme with a higher bit rate. Further, MCS determining section 157determines the number of transmission symbols to be generated from anitem of transmission data in modulation section 102 and repetitionsection 103. Then MCS determining section 157 reports the determinednumber of transmission symbols and determined modulation scheme tosymbol combination/bit combination instructing section 158 and controlinformation generating section 166.

Symbol combination/bit combination instructing section 158 obtains thenumber of constellation patterns used in the received OFDM signal andthe number of replications in a single constellation pattern, from thecontrol channel signal inputted from reception RF section 152, reportsthe obtained number of replications for a single constellation patternto number of symbols for combination instructing section 159, andfurther reports the obtained number of constellation patterns and themodulation scheme reported from MCS determining section 157 toconstellation pattern instructing section 161.

Number of symbols for combination instructing section 159 instructssymbol combining section 163 to perform symbol combination on receptionsymbols on a basis of the number of replications in the singleconstellation pattern.

Based on the modulation scheme and the number of constellation patternsreported from symbol combination/bit combination instructing section158, constellation pattern instructing section 161 reports allconstellation patterns included in a combination of constellationpatterns corresponding to the modulation scheme and the number ofconstellation patterns to bit likelihood calculating section 164, andinstructs bit likelihood calculating section 164 to demodulate receptionsymbols using all those reported constellation patterns.

Symbol deinterleaving section 162 deinterleaves the reception symbolinputted from FFT section 154, converts the deinterleaved receptionsymbol from the parallel signal to a serial signal, and inputs theconverted reception symbol to symbol combining section 163.

Symbol combining section 163 performs symbol combination on thereception symbol inputted from symbol deinterleaving section 162 on abasis of the number of the single constellation pattern reported fromnumber of symbols for combination instructing section 159. Then, symbolcombining section 163 inputs the symbol-combined reception symbol to bitlikelihood calculating section 164.

Using the constellation pattern reported from constellation patterninstructing section 161, bit likelihood calculating section 164demodulates the reception symbol after symbol combination. Further, bitlikelihood calculating section 164 performs bit combination on thedemodulated reception symbol on a basis of the number of constellationpatterns reported from constellation pattern instructing section 161.For example, when four constellation patterns are reported, bitlikelihood calculating section 164 performs bit combination every fourconstellation patterns. Then, bit likelihood calculating section 164makes a soft decision on the reception symbol after bit combination,calculates likelihood per bit (bit likelihood) based on the softdecision value, makes a hard decision based on the calculated bitlikelihood to generate reception data, and inputs the generatedreception data to error correction decoding section 165.

Using an error correction decoding scheme corresponding to the errorcorrection coding scheme used in error correction coding section 101,error correction decoding section 165 performs error correction decodingon the reception data inputted from bit likelihood calculating section164, and inputs the reception data after error correcting decoding to,for example, a baseband section (not shown).

Control information generating section 166 generates a controlinformation signal including the modulation scheme and the number oftransmission symbols generated from an item of transmission datareported from MCS determining section 157 and the measurement result ofthe dispersion of reception quality reported from reception qualitydispersion measuring section 156, and inputs the generated controlinformation signal to transmission RF section 167.

Transmission RF section 167 has, for example, a digital/analogconverter, low noise amplifier and band pass filter, performspredetermined radio transmission processing on the control informationsignal inputted from control information generating section 166, andtransmits the processed control information signal to radio transmissionapparatus 100 via antenna element 151.

Next, the operations of radio transmission apparatus 100 and radioreception apparatus 150 will be described with reference to FIGS. 4, 5and 6A to 6C.

FIG. 4 shows an example of a series of signal processing of transmissiondata from being transmitted from radio transmission apparatus 100 tobeing generated as reception data in radio reception apparatus 150. Inthe example as shown in FIG. 4, it is assumed that modulation section102 uses two constellation patterns and generates two transmissionsymbols and repetition section 103 replicates each of the twotransmission symbols once and generates total four transmission symbols.

In the example as shown in FIG. 4, first, modulation section 102modulates the transmission data using two constellation patterns (a) and(b), thereby generating transmission symbols (a) and (b). Next,repetition section 103 replicates each of the transmission symbols (a)and (b) once, and generates two transmission symbols (a) and twotransmission symbols (b), that is, total four transmission symbols.Then, component parts of radio transmission apparatus 100 generate asingle OFDM signal comprised of the four transmission symbols, andtransmit this radio OFDM signal to radio reception apparatus 150.

Then, radio reception apparatus 150 receives the OFDM signal subjectedto influence of multipath fading on the propagation path. Next,component parts in radio reception section 150 generate two receptionsymbols (a) and two reception symbols (b) from the OFDM signal, that is,total four reception symbols. In FIG. 4, sizes of the generated fourreception symbols are different from one another. This is because thesymbols are subjected to influence such as fading on the propagationpath. Then, symbol combining section 163 performs symbol combination onthe two reception symbols (a), and further performs symbol combinationon the two reception symbols (b). Next, bit likelihood calculatingsection 164 demodulates the reception symbol (a) and reception symbol(b) subjected to symbol combination, performs bit combination, therebygenerating reception data.

FIG. 5 shows three combinations (MCS numbers 1 to 3) of the number ofconstellation patterns used in modulation section 102 and the number ofreplications (number of replications after replication) by repetitionsection 103 when MCS determining section 157 determines that 16QAM is amodulation scheme to be used in radio transmission apparatus 100 and thenumber of transmission symbols to be generated from an item oftransmission data is four. In addition, it is assumed that the codingrate in error correction coding section 101 is R=1/3 in all of MCSnumbers 1 to 3.

As is evident from FIG. 5, in MCS number 1, modulation section 102 usesone constellation pattern, and repetition section 103 makes fourreplications of a transmission symbol by this constellation pattern.Similarly, in MCS number 2, modulation section 102 uses twoconstellation patterns, and repetition section 103 makes tworeplications of transmission symbols by these two constellation patternsrespectively—that is, total four symbols. Similarly, in MCS number 3,modulation section 102 uses four constellation patterns, and repetitionsection 103 does not make replications of these transmission symbols.

Further, as described above, when the dispersion of reception quality ofthe received signal is large, the diversity gain is easier to obtain insymbol combination than in bit combination, and when the dispersion ofthe reception quality is small, the diversity gain is easier to obtainin bit combination than in symbol combination. Therefore,repetition/constellation pattern ratio determining section 113preferably adopts MCS number 2 and MCS number 1 rather than MCS number 3when the dispersion of the reception quality reported from controlinformation extracting section 112 increases, and adopts MCS number 2and MCS number 3 rather than MCS number 1 when the dispersion of thereception quality decreases.

FIGS. 6A to 6C show mapping positions on the IQ plane for fourconstellation patterns (a) to (d) that are usable in modulation by16QAM. FIGS. 6A to 6C further show combinations of constellationpatterns used for total four transmission symbols generated bymodulation section 102 and repetition section 103. More specifically,FIG. 6A shows a mode where four constellation patterns (a) are combinedin a case of MCS number 1. Similarly, FIG. 6B shows a mode where twoconstellation patterns (a) and two constellation patterns (b) arecombined in a case of MCS number 2. FIG. 6C shows a mode whereconstellation patterns (a) to (d) are combined in a case of MCS number3.

Here, with respect to constellation patterns usable in modulation by16QAM as shown in FIGS. 6A to 6C, constellation pattern (a) will bedescribed in detail as an example. When a bit mapping order of atransmission symbol is “i₁, q₁, i₂, q₂,” soft decision are made on twohigher-order bits “i₁, q₁” using a determination threshold of a range of“i₁” in the figure for the in-phase component, and further using adetermination threshold of a range of “q₁” in the figure for thequadrature component. Meanwhile, soft decisions are made on twolower-order bits, “i₂, q₂” using a determination threshold of a range of“i₂” for the in-phase component, and further using a determinationthreshold of a range of “q₂” for the quadrature component. Accordingly,as is evident from FIGS. 6A to 6C, the ranges of the determinationthresholds of two lower-order bits, “i₂, q₂”, are smaller than theranges of the determination thresholds of two higher-order bits, “i₁,q₁”, and it is understood that two lower-order bits are easier to besubjected to influence such as fading and to cause bit errors than twohigher-order bits.

Therefore, in the present invention, transmission data is modulated andreplicated using a plurality of constellation patterns, higher-orderbits and lower-order bits are thereby exchanged to generate a pluralityof transmission symbols. Further, these transmission symbols aretransmitted in a single radio multicarrier signal, and the diversitygain by bit combination is thus obtained to compensate for weak errortolerance of lower-order bits.

Thus, according to the present invention, transmission data is modulatedand replicated using a plurality of constellation patterns to generate aplurality of transmission symbols, the generated transmission symbolsare transmitted in a single OFDM signal, so that it is possible for thereceiving side to obtain the diversity gain in the frequency domain.

Further, according to the present invention, symbol combination and bitcombination are both performed on the received OFDM signal, so that evenwhen the dispersion of reception quality of the OFDM signal is large,the diversity gain can reliably be obtained.

Furthermore, according to the present invention, transmission data ismodulated using all of the four constellation patterns usable in 16QAM,so that the diversity gain is effectively improved on the receiving sidewhen the dispersion of reception quality is small.

Still furthermore, according to the present invention, the number ofconstellation patterns and the number of replications (number ofrepetitions) are determined based on the dispersion of receptionquality, so that the diversity gain can reliably be obtainedirrespective of the degree of the dispersion of reception quality.

Moreover, according to the present invention, the number ofconstellation patterns is adaptively adjusted according to thedispersion of reception quality, so that the diversity gain can reliablybe obtained even when the dispersion of reception quality varies, thatis, the propagation path condition varies.

In addition, although a case has been described in the above-mentionedembodiment where the coding rate is fixed to R=1/3, the presentinvention is not limited to this case, and, for example, MCS determiningsection 157 may decrease the coding rate to improve the bit error ratewhen the reception quality decreases, and increase the coding rate toimprove throughput when the reception, quality increases based on themeasurement result of the reception quality in reception qualitymeasuring section 155.

Further, although a case has been described in the above-mentionedembodiment where the transmission data is modulated in modulationsection 102 and then replicated in repetition section 103 in radiotransmission apparatus 100, the present invention is not limited to thiscase, and, for example, modulation section 102 and repetition section103 may be exchanged in configuration so that repetition section 103first replicates the transmission data up to the number of transmissionsymbols generated from an item of transmission data determined in MCSdetermining section 157, and modulation section 102 modulates thereplicated transmission data sequentially with the specifiedconstellation pattern.

Furthermore, although a case has been described in the above-mentionedembodiment where repetition/constellation pattern ratio determiningsection 113 determines both the number of constellation patterns to beused in modulation section 102 and the number of replications byrepetition section 103, the present invention is not limited to thiscase, and for example, MCS determining section 157 may determine thenumbers directly. In this way, radio transmission apparatus 100 does nothave to report these numbers to radio reception apparatus 150, and it ispossible to improve throughput.

Still furthermore, although a case has been described in theabove-embodiment where repetition/constellation pattern ratiodetermining section 113 adjusts the ratio of the number of constellationpatterns to be used in modulation section 102 and the number ofreplications by repetition section 103 based on the modulation schemeand the dispersion of reception quality reported from controlinformation extracting section 112, the present invention is not limitedto this case, and, for example, the ratio of the number of constellationpatterns to be used in modulation section 102 and the number ofreplications by repetition section 103 may be fixed. In this way, aplurality of component parts can be halted in radio transmissionapparatus 100 and radio reception apparatus 150, so that it is possibleto reduce loads and power consumption of signal processing in theseapparatuses.

Moreover, although a case has been described in the above-mentionedembodiment where the constellation patterns (a) and (b) are combined asshown in FIG. 6B when modulation section 102 modulates transmission datausing two constellation patterns in 16QAM, the present invention is notlimited to this case, and for example, constellation patterns (a) and(c), constellation patterns (a) and (d), constellation patterns (b) and(c), constellation patterns (b) and (d), or constellation patterns (c)and (d) may be combined, respectively.

In addition, although a case has been described in the above-mentionedembodiment where four constellation patterns are used in 16QAM, it isalso possible to use six constellation patterns in 64QAM, and eightconstellation patterns in 256QAM.

Further, the present invention is applicable to not only frequencydivision multiplexing such as OFDM but also time division multiplexing,spatial division multiplexing and code division multiplexing. When thepresent invention is applied to time division multiplexing, it ispossible to response to the dispersion of reception quality caused byfluctuation of reception power in the time domain due to a fast move ofa communication terminal apparatus. Further, when the present inventionis applied to spatial division multiplexing, it is possible to responseto the dispersion of reception quality caused by a difference in qualitybetween streams due to multipath channel. Furthermore, when the presentinvention is applied to code division multiplexing, it is possible toresponse to the dispersion of reception quality caused by intersymbolinterference.

Furthermore, a case has been described as an example in theabove-mentioned embodiment where the present invention is configured byhardware, the present invention can be implemented by software.

In addition, each of functional blocks employed in the description ofthe above-mentioned embodiment may typically be implemented as an LSIconstituted by an integrated circuit. These are may be individual chipsor partially or totally contained on a single chip. “LSI” is adoptedhere but this may also be referred to as an “IC”, “system LSI”, “superLSI”, or “ultra LSI” depending on differing extents of integration.

Further, the method of integrating circuits is not limited to the LSI's,and implementation using dedicated circuitry or general purposeprocessor is also possible. After LSI manufacture, utilization of FPGA(Field Programmable Gate Array) or a reconfigurable processor whereconnections or settings of circuit cells within an LSI can bereconfigured is also possible.

Furthermore, if integrated circuit technology comes out to replace LSI'sas a result of the advancement of semiconductor technology or derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application in biotechnology isalso possible.

The present application is based on Japanese Patent Application No.2004-140968 filed on May 11, 2004, the entire content of which isexpressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is useful, for example, as a base stationapparatus and communication terminal apparatus that are components of amulticarrier communication system.

1. A radio transmission apparatus comprising: a modulation section thatmodulates the same data using a plurality of constellation patternshaving different bit mapping orders to generate a plurality of symbols;a repetition section that performs repetition on the plurality ofsymbols; a generation section that generates a multicarrier signalcomprised of the plurality of symbols subjected to the repetition; and atransmission section that transmits the multicarrier signal.
 2. Theradio transmission apparatus according to claim 1, wherein themodulation section changes the number of constellation patterns used forthe modulation according to dispersion of reception quality measured ona receiving side of the multicarrier signal.
 3. The radio transmissionapparatus according to claim 1, wherein the modulation section decreasesthe number of constellation patterns when the dispersion increases, andincreases the number of constellation patterns when the dispersiondecreases.
 4. The radio transmission apparatus according to claim 1,wherein the repetition section changes the number of repetitionsaccording to dispersion of reception quality measured on a receivingside of the multicarrier signal.
 5. The radio transmission apparatusaccording to claim 1, wherein the repetition section increases thenumber of repetitions when the dispersion increases, and decreases thenumber of repetitions when the dispersion decreases.